Syllogism MCQs for UPSC Prelims

67 practice questions on Syllogism from the Logical Reasoning section of the UPSC Prelims syllabus. 67 come with a written explanation and 20 are actual previous year questions. Try the sample set below - the answer stays hidden until you ask for it.

8 Easy 48 Medium 11 Hard 20 from past papers

Sample questions

Q1
Previous year question medium

Two Statements are given followed by two Conclusions: Statements: All cats are dogs. All cats are black. Conclusion-I: All dogs are black. Conclusion-II: Some dogs are not black. Which of the above Conclusions logically follows/follow from the two given Statements, disregarding commonly known facts?

  1. A Only Conclusion-I
  2. B Only Conclusion-II
  3. C Neither Conclusion-I nor Conclusion-II
  4. D Both Conclusion-I and Conclusion-II
Show answer and explanation

Correct answer: C - Neither Conclusion-I nor Conclusion-II

From 'all cats are dogs' and 'all cats are black', we only know that the cats (a subset of dogs) are black. The colour of dogs that are not cats is undetermined. Conclusion-I (all dogs are black) need not hold, because non-cat dogs might be any colour. Conclusion-II (some dogs are not black) also need not hold, because it is possible that every dog happens to be black. Since each conclusion is only a possibility and not a certainty, neither follows.

Q2
Previous year question medium

Consider the following statements followed by two conclusions: Statements: Some men are great. Some men are wise. Conclusion I: Men are either great or wise. Conclusion II: Some men are neither great nor wise. Which one of the following is correct?

  1. A Only conclusion I is valid.
  2. B Only conclusion II is valid.
  3. C Both the conclusions are valid.
  4. D Neither of the conclusion is valid.
Show answer and explanation

Correct answer: D - Neither of the conclusion is valid.

The premises are particular: 'some men are great' and 'some men are wise'. Conclusion I claims all men are either great or wise, which is a universal claim not supported by two 'some' statements, so it is invalid. Conclusion II claims some men are neither great nor wise, but the premises do not guarantee the existence of such men (the great and the wise could together cover all the men referred to), so it is only a possibility, not a certainty, and is therefore invalid. Since neither follows necessarily, the answer is that neither conclusion is valid.

Q3
Previous year question medium

Three Statements followed by three Conclusions are given below. You have to take the Statements to be true even if they seem to be at variance from the commonly known facts. Read all the Conclusions and then decide which of the given Conclusions logically follows/follow from the Statements, disregarding the commonly known facts : Statement-1 : Some doctors are teachers. Statement-2 : All teachers are engineers. Statement-3 : All engineers are scientists. Conclusion-I : Some scientists are doctors. Conclusion-II : All engineers are doctors. Conclusion-III : Some engineers are doctors. Which one of the following is correct?

  1. A Only Conclusion-I
  2. B Only Conclusion-II
  3. C Both Conclusion-I and Conclusion-III
  4. D Both Conclusion-I and Conclusion-II
Show answer and explanation

Correct answer: C - Both Conclusion-I and Conclusion-III

Given Some doctors are teachers, All teachers are engineers, All engineers are scientists: the doctors who are teachers are therefore engineers and also scientists, so Some scientists are doctors (Conclusion I) follows and Some engineers are doctors (Conclusion III) follows. Conclusion II, All engineers are doctors, does not follow, because only some doctors are linked into the engineer set, not the whole engineer set into doctors. Hence both I and III follow.

Q4
Previous year question medium

Each of the following two items consists of four statements. Of these four statements, two cannot both be true, but both can be false. Study the statements carefully and identify the two that satisfy the above condition. Examine the following statements: 1. All animals are carnivorous. 2. Some animals are not carnivorous. 3. No animals are carnivorous. 4. Some animals are carnivorous. Which two statements satisfy the condition? (a) 1 and 3 (b) 1 and 2 (c) 2 and 3 (d) 3 and 4

  1. A 1 and 3
  2. B 1 and 2
  3. C 2 and 3
  4. D 3 and 4
Show answer and explanation

Correct answer: A - 1 and 3

Two statements that cannot both be true but can both be false are contraries (the universal affirmative 'All A are B' and the universal negative 'No A is B'). Statement 1 (All animals are carnivorous) and statement 3 (No animals are carnivorous) cannot both be true; yet both are false if some animals are carnivorous and some are not. The other pairs are contradictories (1 and 2, or 3 and 4), which cannot both be false. Hence the answer is 1 and 3.

Q5
Previous year question medium

Consider the following Statements and Conclusions: Statements: 1. Some rats are cats. 2. Some cats are dogs. 3. No dog is a cow. Conclusions: I. No cow is a cat. II. No dog is a rat. III. Some cats are rats. Which of the above conclusions is/are drawn from the statements?

  1. A I, II and III
  2. B Only I and II
  3. C Only III
  4. D Only II and III
Show answer and explanation

Correct answer: C - Only III

Conclusion III is the simple converse of statement 1: 'Some rats are cats' immediately gives 'Some cats are rats' (a valid conversion of a particular affirmative), so III follows. Conclusion I ('No cow is a cat') does not follow: from 'No dog is a cow' and 'Some cats are dogs', the cats that are not dogs could still be cows, so a definite negative between cow and cat cannot be drawn. Conclusion II ('No dog is a rat') does not follow either: 'Some rats are cats' and 'Some cats are dogs' need not connect rats and dogs, but they also do not exclude them, so no definite negative holds. Only III is valid, option (c).

Q6
Previous year question medium

Examine the following statements: 1. None but students are the members of the club. 2. Some members of the club are married. 3. All married persons are invited for dance. Which one of the conclusions can be drawn from the above statements?

  1. A All students are invited for dance.
  2. B All married students are invited for dance.
  3. C All members of the club are married persons.
  4. D None of the above conclusions can be drawn.
Show answer and explanation

Correct answer: D - None of the above conclusions can be drawn.

Statement 1 means every club member is a student, but NOT that every student is a member. (a) fails: not all students are married, so not all are invited for dance. (b) fails: a married student need not be a club member (the link to 'married' runs through club members, and only some members are married); we cannot conclude all married students are invited. (c) fails directly: only 'some' members are married, not all. Since none of (a), (b) or (c) necessarily follows, the answer is (d).

Q7
Previous year question medium

Consider the following statements: 1. All X-brand cars parked here are white. 2. Some of them have radial tyres. 3. All X-brand cars manufactured after 1986 have radial tyres. 4. All cars are not X-brand. Which one of the following conclusions can be drawn from the above statements?

  1. A Only white cars are parked here.
  2. B Some white X-brand cars with radial tyres are parked here.
  3. C Cars other than X-brand cannot have radial tyres.
  4. D Most of the X-brand cars are manufactured before 1986.
Show answer and explanation

Correct answer: B - Some white X-brand cars with radial tyres are parked here.

From statement 1, all X-brand cars parked here are white. From statement 2, some of these (white, X-brand, parked here) cars have radial tyres. Combining, some white X-brand cars parked here have radial tyres, which is exactly option (b). Option (a) overreaches: statement 4 allows non-X-brand cars parked here that may not be white. Option (c) is unsupported: nothing says non-X-brand cars cannot have radial tyres. Option (d) is unsupported by any statement. Hence (b).

Q8
Previous year question medium

Examine the following statements: 1. Only those who have a pair of binoculars can become the members of the birdwatcher's club. 2. Some members of the birdwatcher's club have cameras. 3. Those members who have cameras can take part in photo-contests. Which of the following conclusions can be drawn from the above statements?

  1. A All those who have a pair of binoculars are members of the birdwatcher's club.
  2. B All members of the birdwatcher's club have a pair of binoculars.
  3. C All those who take part in photo-contests are members of the birdwatcher's club.
  4. D No conclusion can be drawn.
Show answer and explanation

Correct answer: B - All members of the birdwatcher's club have a pair of binoculars.

Statement 1 says 'only those who have a pair of binoculars can become members', meaning having binoculars is a necessary condition for membership. Therefore every member must possess a pair of binoculars, which is exactly (b). (a) reverses this - having binoculars does not make someone a member. (c) is not given - non-members might also take part in photo-contests, and statement 3 only links member-camera-owners to contests. Since (b) is a valid conclusion, (d) is wrong.

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More Logical Reasoning topics

Logical Deductions 171 Puzzles & Arrangements 100 Ranking & Ordering 90 Coding-Decoding 89 Number & Letter Series 83 Counting & Combinatorial Reasoning 77 Analogy & Classification 67 Blood Relations 67 Statement & Conclusions 63 Direction Sense 62 Venn Diagrams 62 Seating Arrangement 49 Statement & Assumptions 46 Cubes & Dice 45 Statement & Arguments 42